sql.py: Added insert_select() and use it in insert()

Calls to sql.esc_name*(): Removed preserve_case=True because it is now the default

sql.py: esc_name_by_module(): Changed preserve_case to ignore_case, which defaults to False

Calls to sql.esc_name*(): Removed preserve_case=True because it is now the default

sql.py: esc_name_by_module(): preserve_case defaults to True

sql.py: mk_select(): Escape all names used (table, column, cond, etc.)

sql.py: esc_name_by_module(): If not enclosing name in quotes, call check_name() on it

sql.py: mk_select(): Support literal values in the list of cols to select

sql.py: mk_select(): Don't escape the table name, because it will either be check_name()d or it's already been escaped

sql.py: Added mk_select(), and use it in select()